


A Lesson on Female Anatomy and Breeding

by Dark_Crystal_Demon



Series: Undertail University [1]
Category: Undertale (Video Game)
Genre: Anatomy, Breeding, Clinical Gaster, Consensual Kink, Consensual Sex, Ecto-Penis (Undertale), Explaining Hybrid Creation, F/M, Hybrids, Impregnation, Knotting, Professor Gaster, Vibrators, Voyeurism
Language: English
Status: Completed
Published: 2016-12-04
Updated: 2016-12-04
Packaged: 2018-09-06 08:43:37
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 1,490
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/8743144
Author URL: https://archiveofourown.org/users/Dark_Crystal_Demon/pseuds/Dark_Crystal_Demon
Summary: Gaster gives lessons on breeding by using human volunteers for his demonstrations.Many of his students believe this is just an excuse to create his own league of hybrids....They would be right.But no one's complaining about the class.





	

**Author's Note:**

> Inspired by the amount of NSFW audio I've been reading on Tumblr.  
> I thought about what something with a clinical Gaster would sound like...

Good afternoon, class. I see we have a full house today. Excellent. Today we're going to be exploring the anatomy of the human, female body for the purposes of breeding.

Because I'll be using a live subject, there will be no video footage of this class. However, audio recording and note-taking are permitted and encouraged.

Our subject standing here has given permission for us to view her naked as she is now. However, to protect her identity, she will continue to wear the blindfold, and will be referred to simply as human.

The watch on her wrist will be monitoring her heart rate. I will also direct you to observe her soul during certain times within the demonstration.

Most human souls can be found here, at the solar plexus, just below their rib cage-

My, my, she is a hypersensitive one, isn't she? Notice how she shivers under my touch? In humans, this is a good sign of attraction. We've also chosen her during the peak season for fertility. With her body biologically ready to accept sperm, our chances of conception will rise.

Yes? In the back?

Ah, good question. According to our studies so far, female monsters who create magical appendages have had just as much success rate with female human hosts. Human eggs seem to accept most magical sperm, no matter the source. However, they do not seem to be able to create male offspring when mating with another female.

Notice how I have kept touching the human as I talked? Keeping a female human stimulated is the key to effective copulation.

Observe on the monitor how her heart rate increases with my simple caresses? For those of you that can't feel heart beats as easily, watch for the rise in her chest. See how much higher her chest rises? The long breaths are accommodating her quickening heart beat.

Now, not every human will react this way. Some need more forceful stimulation. You could claw your fingers across her sides, like so-

Ah, see how she bites her lip? That is a form of human modesty. Many humans are raised with this reflexive reaction. Even humans that volunteer to be models in breeding demonstrations.

Human, I know I instructed you not to talk, but I will need you to allow yourself to vocalize your pleasure for the demonstration.

Now if I reach around her and rake my fingers down her back-

 _Aaaaaah_!

Yes, thank you. Perfect, human.

Her nipples have risen beautifully. See how defined they are now? You can cup the entire breast, like so, and -look how her lips parted from my fondling. Many humans enjoy kissing and attention to their lips, especially at the beginning and at the end of a breeding session. In the beginning, this also gives the human time to prepare themselves for your entry.

For the sake of time, I'll be using more aggressive techniques to get the human ready. Circling the areola and then pinching the nipple will get you a faster response.

_ah. Ah. AH!_

She's getting louder because I'm applying more pressure. Most female humans can't feel you touch their nipples unless you apply some force.

Excellent, her skin is warming up marvelously, which will be good for initial incubation of your sperm. See the flush of her cheeks and the steady but quick heart beat? You'll want her to stay at this level of stimulation.

Biting, licking, or massaging female erogenous zones will help. Now that we have a living model, let me highlight a few key areas. Pay attention to her heart rate as I use my tongue and hands to stimulate this spot behind her ear...

 _Aaaaah_...

the nape of her neck...

 _Yaaaa_......

We've already covered the breasts, so let's caress the shoulder to the back of her neck and down her spinal column...

 _Mmmm....aaaaAAAH_!

Not every human will react so well to getting their glut slapped; however, this one has already shown that she enjoys a rougher approach.

The inner thigh is extremely sensitive-

Hm, yes?

**Well aren't you an impatient monster.**

**If breeding a human was as easy as sticking your penis inside her vagina, do you think I would be teaching this class? You ignorant, worthless, pile of dust.**

Look at that, you've distracted the human. Let me place her down on the table and start stimulating her clitoris while I explain to this dust cloud that hybrids are the most powerful beings nature can create. They're rare occurrences since they require female humans with specific qualities.

 _aaaa_...

Good girl. You see, the perfect vessel for magical offspring is a human who is well-attuned to herself. A human female that allows herself pleasure and regularly masturbates is desirable for this procedure.

 _Ooooo_....

However, if you've chosen a human who does not know her own erotic zones, you can easily find them through a bit of exploration. I encourage this part of the mating ritual. The more pleasure you give to the human, the more willing they are to mate with you.

_Ooooo maaaaa iiiiii....._

Notice how she's gripping the table? Her hips raising up into my hand? Willingness is vital for breeding. Not only will you need her soul to consent part of itself during conception; her soul will also be feeding your child throughout the pregnancy to develop it's physical structure.

_Ah. Ah. Ah! AH!_

She's getting close, her legs are shaking. Observe the brightness and strength of her soul. Human hormones can become very unstable during pregnancy, so you'll need to be sure you've chosen a bright soul full of determination.

 _AAAAAHHHH_!

Let me insert my fingers inside and curl them around her Gräfenberg spot. This way I can elongate this orgasm for you to analyze her soul.

 _Ooooooo_ _Gast-_!

As she arches her back and continues to ride this orgasm, observe how her soul is shining brighter than before. She can barely breathe in this state of arousal; her soul is in a state of near death. It's energy is heightened to keep her alive. And if you are to cum right at this moment, that life energy would envelope your seed and fertilize.

And that ends our class lesson unless you'd like to stay for the breeding portion.

Human, do you still want to proceed?

My, you are an eager one.

On the side of this table I've attached a vibrator with a remote control. I'm bending her over it to stimulate her throughout the knotting.

Can you feel the vibrator, human?

 _Mmmm_...

Excellent. Now I will insert myself.

 _Aaaaah_!

She's very tight. Many monsters mistake that for a tight seal. It is not. You need to ride her and let the vibrator do it's job.

You can't see inside her, but I've grown myself to fill her entire vaginal canal. In this way, I can feel the tight barrier wall of her cervix. You focus your thrusts so as not to damage that barrier, but merely press against it. As you do so, her vaginal walls will widen with her arousal from the vibrator and your thrusts.

Female humans can always take more than they originally appear. Slowly widen the girth of your penis inside her.

 _AH_!

Don't worry, human. You're not splitting in half. I'm just revealing your full potential.

_ah. Ah. AH._

Her next orgasm is about to happen. 

Start to form your knot at the base of your penis. 

She'll ride herself along your shaft. Allow her to and continue to grow.

_Oh, yes! Yes!_

Oh.... human. Good girl. Keep that up.

As you... feel her rhythm...

start to lose control...

grab hold of her waist and thrust her over your knot!

 _AHHH_!

Oh, human! AHHH!

...

....

Ahem. 

Notice the dazed look on my human's face. I've been told that for humans, this moment is beyond any orgasm they've ever had. Her heart stopped beating for a full minute as her soul focused on the creation of a second womb within her and the fertilization of my magic.

If her human seed survives, it will fuse with the magic and make a more humanoid hybrid. If it doesn't, only the monster portion will be the dominant physical form. 

For good measure, have your human orgasm again against your knotted cock. She won't be able to move along your shaft, but, as demonstrated earlier, she has the capabilities of an orgasm through clitoral stimulation alone.

The amount of times she orgasms will define how much of her soul energy mixes with your child's creation. Therefore, the more orgasms you make her have, the stronger your offspring will be.

Class is dismissed.

The rest of this simulation will be redundant. You may stay if you are curious about how many orgasms a female human can have, but I warn you   **t h i s   i s   g o i n g   t o   t a k e   a   l o n g   t i m e**.

**Author's Note:**

> What did you think? Let me know in the comments below. 
> 
> Check Out My Tumblr (NSFW): [Dark_Crystal_Demon](https://www.tumblr.com/blog/darkcrystaldemon)
> 
> Or check out some of my other Undertale fics on AO3 like [Heat-tale](http://archiveofourown.org/works/8140172/chapters/18657806) ,an anthology themed around heat cycles and sometimes breeding.


End file.
